Blends of low carbon and conventional fuels with improved performance characteristics

ABSTRACT

The present invention provides a blended fuel and methods for producing the blended fuel, wherein a low carbon fuel derived from a renewable resource such as biomass, is blended with a traditional, petroleum derived fuel. A blended fuel which includes greater than 10% by volume of low carbon fuel has an overall improved lifecycle greenhouse gas content of about 5% or more compared to the petroleum derived fuel. Also, blending of the low carbon fuel to the traditional, petroleum fuel improves various engine performance characteristics of the traditional fuel.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to blended fuels, where a lowcarbon fuel, ideally derived from a production process that uses arenewable, biomass feedstock, is blended with a traditional, petroleumderived fuel. Such blended fuels result in an overall improvedwell-to-wheels greenhouse gas content, as well as improved performancecharacteristics of the fuels, compared to the petroleum derived fuels.

2. Description of Related Art

Global demand for energy continues to rise at a significant rate,particularly among emerging industrialized nations. Biomass and otheralternative carbon resources are becoming more attractive as renewableenergy sources due to increasing energy costs as well as forenvironmental reasons.

Various types of fuels produce different amounts of greenhouse gasesduring their entire lifecycle (e.g., during fuel production,transportation, and consumption). Thus, these fuels have differentimpacts on the environment. One way to compare the greenhouse gas effectof each fuel is by calculating and comparing well-to-wheels greenhousegas content to the well-to-wheels greenhouse gas content of a petroleumfuel (or “baseline” fuel).

A well-to-wheels greenhouse gas content (“WWGGC”) refers to acalculation that is done using a greenhouse gas model, such as ArgonneNational Laboratories GREET model (currently in version 1.8d.1 which canbe downloaded at http://greet.es.anl.gov/) or another similar greenhousegas model. The model allows for the calculation of the amount ofgreenhouse gases that are produced throughout the entire lifecycle ofthe product (from “well to wheels”). The model takes into account, amongother things, the production method, the feedstock used in theproduction, the type of fuel produced, transportation of the fuel tomarket, and the emissions produced from combustion of the fuel when itis used.

Petroleum derived fuels, such as gasoline and diesel fuel that arerefined from oil using a traditional production method, produce a largeamount of greenhouse gases. For example, diesel production from oilresults in a well to well to wheels greenhouse gas production content of383 gCO₂e/mi (all WWGGC scores referenced in this document arecalculated using version 1.8d.1 of the GREET model which can bedownloaded at http://greet.es.anl.gov/ and which provides archives ofall older versions of the software). The units' gCO₂e/mi means the gramsof carbon dioxide equivalent greenhouse gases that result fromtravelling one mile in a vehicle using the fuel. Other fuels, such asfirst generation biofuels (e.g., ethanol derived from corn), also scoreclose to or greater than petroleum derived fuels in terms of WWGGCcalculated according to the GREET model, thus providing no significantWWGGC benefit over petroleum fuels. For example, E85 (meaning 85%ethanol and 15% gasoline, where the ethanol is derived from corn)receives a WWGGC of 358 gCO₂e/mi.

Some of synthetic fuels that are produced from a biomass feedstock,using thermochemical or biochemical conversion processes, can achievelifecycle greenhouse gas scores that are greater than 50% lower thantraditional, petroleum derived fuels (e.g., a WWGGC score of lower than191 using the GREET model). When comparisons are made, the same vehicleis used in the GREET model for comparison. While biofuels produced fromexisting known methods today may achieve an improved WWGGC compared topetroleum fuels, when blended with petroleum fuels, the engineperformance characteristics of the blended fuels are sometimes reducedcompared to the neat petroleum fuels. For example, blending suchsynthetic fuels with the petroleum fuel can reduce the engineperformance characteristics of the petroleum fuel, such as a cetanenumber, lubricity, and increase emissions.

There is a need for an alternative fuel derived from a biomassfeedstock, which when blended with a petroleum fuel, not onlysignificantly improves WWGGC, but also improves the engine performancecharacteristics of the blended fuels. The present invention meets theseneeds as well as others and provides a substantial improvement over theprior art.

SUMMARY OF THE INVENTION

Embodiments of the invention provide a blended fuel which includes apetroleum fuel and a low carbon fuel produced from a renewable biomassfeedstock, where the renewable biomass feedstock is converted into a lowcarbon fuel using a next generation process.

In embodiments of the invention, the low carbon fuel derived from arenewable feedstock has a well-to-wheels greenhouse content (“WWGGC”)which is at least 50% lower than a WWGGC of the petroleum fuel when usedin the same vehicle. When the low carbon fuel, in accordance withembodiments of the invention, is blended at least 10% by volume (withthe rest of the balance from the petroleum fuel), the blended fuel hastwo or more performance characteristics (measurable by ASTM standards)which are improved compared to the 100% petroleum derived fuel. Forinstance, when a low carbon fuel diesel in accordance with the presentinvention and a petro diesel are blended, the blended fuel meets theASTM D975 specification and has improved engine performancecharacteristics, such as better lubricity, higher cetane number, lowersulfur content, and/or enhanced oxidative stability, compared to thepetroleum diesel fuel.

In one aspect of the invention, a blended fuel comprises about 5% toabout 90%, by volume, of a petroleum fuel and about 95% to about 10%, byvolume, of a low carbon fuel produced from a renewable biomassfeedstock. The low carbon fuel is produced by a process where therenewable biomass feedstock is converted into syngas, and then thesyngas is reacted with a catalyst to produce the low carbon fuel.

In one embodiment of the invention, the low carbon fuel has awell-to-wheels greenhouse gas content which is at least about 50% lowerthan a well-to-wheels greenhouse gas content of the petroleum fuel. Thelow carbon fuel also has at least two performance characteristic valuesmeasurable by ASTM tests which are at least about 40% improved comparedto corresponding performance characteristic values of the petroleumfuel. The performance characteristic values include a cetane number,lubricity value, sulfur content, oxidative stability value, and others.

In another embodiment of the invention, the blended fuel has awell-to-wheels greenhouse gas content which is at least 5% lower thanthe well-to-wheels greenhouse gas content of the petroleum fuel. Theblended fuel also has at least two performance characteristic valuesmeasurable by ASTM tests which are at least about 5% improved than thecorresponding performance characteristic values of the petroleum fuel.

In another aspect of the invention, a process for producing a blendedfuel is provided. The process includes converting a renewable biomass(such as forest residues, agricultural wastes, other) feedstock into asyngas and reacting the syngas with a catalyst to produce a low carbonfuel. About 5% to 90%, by volume, of a petroleum fuel and about 10% toabout 95%, by volume, of a low carbon fuel (total 100% volume) areblended together.

In one embodiment, the low carbon fuel has a cetane number of greaterthan about 65. In another embodiment, the low carbon fuel has alubricity value which is less than about 450 microns by HFRR at 60° C.(scar) measured by ASTM D 6079.

In yet another embodiment, the blended fuel has a cetane number that isgreater than 5% or higher than the neat petroleum fuel. In yet anotherembodiment, the blended fuel has a lubricity value which is less thanabout 450 microns by HFRR at 60° C. (scar) measured by ASTM D 6079. Insome embodiments, the blended fuel has a lubricity value which is lessthan about 400 microns or less than 350 microns by HFRR at 60° C. (scar)measured by ASTM D 6079.

Other objects, features, and advantages of the present invention willbecome apparent upon consideration of the following detailed descriptionand the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (100) shows a schematic diagram of a process for making a blendedfuel comprising a petroleum fuel and a low carbon fuel produced from arenewable biomass feedstock.

FIG. 2 (200) shows cetane numbers of blended fuels comprising varyingproportions of a low carbon fuel derived from agricultural wastes and atraditional petroleum diesel fuel #2. The percent (%) of the low carbonfuel blended into petroleum fuel is shown (220) versus the cetane number(210). 100% petroleum fuel represented as California #2 diesel (andblended with no low carbon fuel) (230) has a cetane number of 44. Whenthe low carbon fuel described herein is blended at 25% (with 75%petroleum fuel) the cetane number of the blended fuel is 54 (240). Whenthe low carbon fuel described herein is blended at 50% (with 50%petroleum fuel) the cetane number of the blended fuel is 71 (250). Whenthe low carbon fuel described herein is blended at 75% (with 25%petroleum fuel) the cetane number of the blended fuel is 74 (260) orclose to the same level as the 100% low carbon fuel. At 100% low carbonfuel, the cetane number is 76 (270). It can be seen from the data abovethat blending of the low carbon diesel fuel described herein providesperformance improvement benefits in excess of the improvement expectedfrom the blend level.

FIG. 3 (300) shows HFRR lubricity values (D 6079, wear scar micron) ofblended fuels comprising varying proportions of a low carbon fuelderived from biomass residues with a traditional petroleum diesel(California #2 Fuel). The percent (%) of the low carbon fuel blendedinto petroleum fuel is shown (320) versus the HFRR lubricity values(310). 100% petroleum fuel represented as California #2 diesel (andblended with no low carbon fuel) (330) has a HFRR lubricity value of550. When the low carbon fuel described herein is blended at 25% (with75% petroleum fuel) the HFRR lubricity of the blended fuel is 480 (240).When the low carbon fuel described herein is blended at 50% (with 50%petroleum fuel) the HFRR lubricity of the blended fuel is 420 (250).When the low carbon fuel described herein is blended at 75% (with 25%petroleum fuel) the HFRR lubricity of the blended fuel is 390 (260) orclose to the same level as the 100% low carbon fuel. At 100% low carbonfuel, the HFRR lubricity is 360 (270). It can be seen from the dataabove that blending of the low carbon diesel fuel described hereinprovides performance improvement benefits in excess of the improvementexpected from the blend level.

FIG. 4 (400) shows HFRR lubricity values (D 6079, wear scar micron) ofblended fuels comprising varying proportions of a traditional biodieselderived from vegetable oils with a traditional petroleum diesel fuel #2.The percent (%) of the biodiesel blended into petroleum fuel is shown(420) versus the HFRR lubricity values (410). 100% petroleum fuelrepresented as California #2 diesel (and blended with no biodiesel)(430) has a HFRR lubricity value of 550. When the biodiesel is blendedat 25% (with 75% petroleum fuel) the HFRR lubricity of the blended fuelis still 550 (440). When the low carbon fuel described herein is blendedat 50% (with 50% petroleum fuel) the HFRR lubricity of the blended fuelis 551 (450). When the low carbon fuel described herein is blended at75% (with 25% petroleum fuel) the HFRR lubricity of the blended fuel is547 (560) or close to the same level as the 100% low carbon fuel. At100% low carbon fuel, the HFRR lubricity is 549 (570). It can be seenfrom the data above that blending of biodiesel provides no performanceimprovement. Similar results occur with other performancecharacteristics.

DETAILED DESCRIPTION

Embodiments of the invention provide a blended fuel and a method formaking the blended fuel, where the blended fuel comprises a petroleumfuel blended with at least 10%, by volume, of a low carbon fuel derivedfrom a renewable biomass feedstock. The low carbon fuel in accordancewith embodiments of the invention has a well-to-wheels greenhouse gascontent (“WWGGC”) which is at least about 50% lower than awell-to-wheels greenhouse gas content of the petroleum fuel.

Furthermore, when a low carbon fuel in accordance with embodiments ofthe invention is blended with a petroleum fuel, the low carbon fuelimproves one or more performance characteristics described in thecorresponding ASTM specification for the fuel when compared to thepetroleum fuel. The improved performance characteristics include, forexample, cetane number, lubricity, oxidative stability, and reducedsulfur content. In addition, tailpipe emissions of nitrogen oxides,carbon monoxide, hydrocarbons and particulates may be reduced.

A number of performance characteristics of a fuel can be measured bystandard test methods, such as various ASTM standard tests. For example,for a diesel fuel, a cetane number of the fuel can be tested by astandard test method ASTM D613. The cetane number provides a measure ofthe ignition characteristics of diesel fuel oil in compression ignitionengines. This test method covers the determination of the rating ofdiesel fuel oil in terms of an arbitrary scale of cetane numbers using asingle cylinder, four-stroke cycle, variable compression ratio, andindirect injected diesel engine. The cetane number scale covers therange from zero to 100.

In embodiments of the invention, a low carbon fuel has a cetane numberin the range of 65 to 80 or higher.

Lubricity refers to the ability of a fluid to minimize the degree offriction between surfaces in relative motion under load conditions. Alubricity value of a fuel can be measured by a standard test method,such as ASTM D6079 or D6751. ASTM D6079 is a standard test method forevaluating lubricity of diesel fuels by the high-frequency reciprocatingrig (HFRR). The wear scar generated in the HFRR test is sensitive tocontamination of the fluids, test materials, and the temperature of thetest. It is measured in terms of a diameter of wear scar in microns.

In embodiments of the invention, a low carbon fuel has a HFRR lubricityvalue of less than about 500 microns. More typically, a low carbon fuelin accordance with the present invention has a HFRR lubricity value inthe range from 200-450 microns.

The sulfur content of a fuel can be measured by various standard testmethods, such as ASTM D5453. As of September 2007, most on-highwaydiesel fuel sold at retail locations in the United States is ultra-lowsulfur diesel with an allowable sulfur content of 15 ppm.

In embodiments of the invention, a low carbon fuel has sulfur content ofless than 5 ppm.

The oxidative stability value can be measured by standard test methods,such as ASTM D2274-10. This test method provides a basis for thedetermination of the storage stability of middle distillate such as No.2 fuel oil. A fuel is tested under specified oxidizing conditions at 95°C.

In embodiments of the invention, a low carbon fuel has an oxidativestability value that is greater than 5% improved over traditionalpetroleum derived fuels.

All of these and other suitable ASTM standards can be adopted to testperformance characteristics of fuels in accordance with embodiments ofthe invention. These and other ASTM standard test methods are herebyincorporated by reference in their entirety.

The performance characteristics (e.g., measured by ASTM tests) of a lowcarbon fuel in accordance with the present invention are 5-90% betterthan the corresponding performance characteristic values of a petroleumfuel which is to be blended with the low carbon fuel. By “better” or“improved,” a specific performance characteristic value (e.g., cetanenumber) of a low carbon fuel can be higher or lower than thecorresponding value for a petroleum fuel.

For example, if a petro diesel has a cetane number of 50 and a lowcarbon diesel fuel in accordance with the present invention has a cetanenumber of 70, then the cetane number of the low carbon fuel is 40%better or improved compared to the cetane number of the petroleum fuel.

In another example, if a petro diesel has a lubricity value of 530microns in wear scar and a low carbon diesel fuel in accordance with thepresent invention has a lubricity value of 300 microns, then thelubricity value (in terms of wear scar diameter) of the lower carbonblend is considered 43% better or improved, compared to the lubricityvalue of the petro diesel.

When a low carbon fuel in accordance with the present invention isblended with a petroleum fuel, blending improves at least twoperformance characteristics of a blended fuel by at least 5%, 10%, 15%,20%, 30%, 40%, 50% or more, compared to the corresponding performancecharacteristics of the petroleum fuel.

For example, if a blended fuel is a diesel fuel (e.g., a petro dieselcombined with a low carbon fuel comprising C8+ fraction), thecorresponding ASTM D975 specification includes performancecharacteristics such as lubricity, cetane, sulfur content, oxidativestability, and others. In embodiments of the invention, blending of alow carbon diesel fuel with a petro diesel improve two or more ofperformance characteristics of ASTM D975. For example, if a petro dieselhas a cetane number of 50 and a low carbon diesel in accordance with thepresent invention has a cetane number of 70, a 15% blend (i.e., 15% lowcarbon diesel and 85% petro diesel) has a cetane number of 53, which is6% better or improved compared to the cetane number of the petro diesel.

As used herein, the terms “a petroleum derived fuel” or “petroleum fuel”refers to a fuel derived from a fraction or fractions of a petroleumcrude oil.

The term “diesel fuel” refers to any liquid fuel used in diesel engines.A diesel fuel includes a mixture of carbon chains that typically containbetween 8 to 24 carbon atoms per molecule. A conventional diesel fuel isa petroleum derived diesel fuel or petro diesel which is a distillatefrom crude oil obtained by collecting a fraction boiling at atmosphericpressure over an approximate temperature range of 200° C. to 350° C.degrees. A diesel fuel may also include a synthetic diesel derived fromalternative sources (e.g., renewable biomass).

The term “renewable biomass feedstock” refers to any organic matter thatis available on a renewable or recurring basis, including renewableplant materials (feed grains, other agricultural commodities, otherplants and trees, algae), waste material (crop residue, other vegetativewaste material including wood waste and wood residue), animal waste andbyproducts (fats, oils, greases, and manure), construction waste, andfood waste/yard waste. The term “renewable biomass feedstock” refers toany of the above materials and excludes those obtained from petroleumcrude oil.

The term “well-to-wheels greenhouse gas content” refers to a calculationthat is done using a greenhouse gas model, such as Argonne NationalLaboratories GREET (“Greenhouse gases, Regulated Emissions, and EnergyUse in Transportation”) model or another similar greenhouse gas model,that allows for the calculation of the amount of greenhouse gases thatare produced throughout the entire lifecycle of the product (from “wellto wheels”). The model takes into account among other things theproduction method, the feedstock used in the production, the type offuel produced, transportation of the fuel to market, and the emissionsproduced from combustion of the fuel when it is used.

The most recent version of GREET includes more than 100 fuel pathwaysincluding petroleum fuels, natural gas fuels, biofuels, hydrogen andelectricity produced from various energy feedstock sources. The mostrecent versions of GREET model (GREET 1.8d1 for fuel-cycle model andGREET 2.7 for vehicle-cycle model which calculates the life-cycle energyuse emissions for vehicle production) is available athttp://greet.es.anl.gov/. The software for calculating WWGGC is readilyavailable and can be downloaded by the public. The GREET model can beused to calculate the energy use and greenhouse gas (GHG) emissionsassociated with the production and use of a particular type of fuel.

The WWGGC calculations include two parts. First, a well-to-tank (WTT)life cycle analysis of a petroleum based fuel pathway includes all stepsfrom crude oil recovery to final finished fuel. Second, a tank-to-wheel(TTW) analysis includes actual combustion of fuel in a motor vehicle formotive power. The WTT and TTW analyses are combined to provide a totalwell-to-wheel (WTW) analysis, which provides a calculation for awell-to-wheel greenhouse gas content (“WWGGC”). The WWGGC units may beexpressed in CO₂ equivalents per any convenient energy unit as long asthe same units are used throughout the life cycle analysis. The WWGGCunits may be expressed in CO₂ equivalents per any convenient energy unitas long as the same units are used throughout the life cycle analysis.

Thus, using the GREET or other models for calculating WWGGC, a WWGGCscore of a particular fuel can be compared with a petroleum derived fuelsuch as gasoline or petro diesel. The lower the WWGGC, the lower theamount of greenhouse gas a particular fuel produces during itslifecycle. For example, diesel production from oil results in a well towell to wheels greenhouse gas production content of 383 gCO₂e/mi (allWWGGC scores referenced in this document are calculated using version1.8d.1 of the GREET model). The units' gCO₂e/mi means the grams ofcarbon dioxide equivalent greenhouse gases that result from travellingone mile in a vehicle using the fuel. Gasoline when derived frompetroleum receives a score of 447 gCO₂e/mi. Biomass derived diesel fuelsusing processes described herein, receive a score of about 49 gCO₂e/mi(or 87% less than petro diesel when used in the same vehicle type). Theactual score for the biomass derived fuels will depend on modificationsto the GREET model that relate to the actual process used in theproduction of the fuel as well as other variables, for example theproject location, type of feedstock used, and technical informationrelated to the actual process used.

The term “a low carbon fuel” refers to a fuel derived from a renewablebiomass feedstock with a WWGGC which is at least about 50% less than aWWGGC of a petroleum fuel or a petroleum baseline. In some embodiments,a low carbon fuel can have a WWGGC which about 60%, 70%, 80%, or 90%less than the petroleum baseline. A low carbon fuel may be in anysuitable form, such as a diesel fuel, gasoline, kerosene, aviation fuel,and others.

Fuels derived from biomass do not necessarily have a lower WWGGCcompared to the petroleum baseline. First generation biofuels, such asethanol derived from corn or other feedstocks, also typically scoreclose to or greater than their petroleum derived counterparts. Forexample, E85 (meaning 85% ethanol and 15% gasoline, where the ethanol isderived from corn) receives a WWGGC of 358 gCO₂e/mi.

While renewable fuels, such as biodiesel and bioethanol, can providesome benefit in reducing WWGGC when these fuels are blended withconventional petroleum fuels, these renewable fuels can negativelyimpact their engine performance characteristics. For example, blendingof bioethanol with traditional diesel fuel, lowers the cetane number ofa diesel fuel, negatively impacting its engine combustion quality. Evenwhen blended at 20% ethanol, the cetane number of the diesel fuel barelymeets engine performance specifications.

Furthermore, biodiesel which typically has a cetane number between 40and 55 will either have no impact or a detrimental impact on cetanenumber.

In embodiments of the invention, renewable biomass feedstocks areprocessed in a suitable system to produce a unique synthetic, low carbonfuels. In certain embodiments, low carbon fuels are diesel fuels fromwaste biomass. Low carbon fuels according to the invention provide amajor improvement in WWGGC over the petroleum fuel baseline and alsoprovide an improvement in various performance characteristics, such ascetane number, lubricity and/or reduced tailpipe emissions.

Biomass or other renewable resources can be converted into liquid fuelsusing biochemical or thermochemical approaches.

Using thermochemical conversion processes, biomass or other renewableresources can be converted into syngas using gasification,pyrolysis/steam reforming, and other methods. After conversion tosyngas, the syngas can be catalytically converted into a wide variety ofliquid fuels. Other thermochemical processes include the production ofliquid fuels from pyrolysis oils, hydroprocessing of waste animal fats,and other thermochemical processes.

Using biochemical conversion processes, biomass or other renewableresources can be converted to sugars using various enzymes. Afterconversion to sugars, the sugars can be converted to ethanol or otherfuels, chemicals, or intermediaries using conventional microorganismfermentation processes, or possibly to other fuels, chemicals orintermediaries using modified microorganism strains.

In one embodiment, a blended fuel may include a synthetic fuel which isa low carbon fuel derived from biomass derived sugars. The process usesan engineered yeast to convert sugar to isoprenoids. These intermediaryisoprenoids are then processed into final fuel products that are used asa blendstock.

In one embodiment, a blended fuel may include a synthetic diesel fuelwhich is a low carbon fuel derived from a renewable biomass feedstockand a petro diesel. In another embodiment, a synthetic diesel fuel is anon-ester, renewable diesel fuel. Such blended fuels may meet thestandards and specifications detailed in ASTM D975, which is the samestandards and specifications for petro diesel fuels. Contrary to asynthetic diesel in accordance with the present invention, a biodiesel(i.e., a fuel comprised of mono-alkyl esters of long chain fatty acidsderived from vegetable oils or animal fats) and its blends must meet thespecifications of a different standard, ASTM D 6751.

In another embodiment, the blended fuel may include a low carbon fuelwhich is comprised of a non-ethanol or non-alcohol hydrocarbon fuel.

Embodiments of the invention provide for a number of advantages. Forexample, blending a low carbon fuel according to the present inventionwith a petroleum fuel reduces the world's dependence on fossil fuelsproduced from petroleum crude oil. A low carbon diesel fuel and itsblend according to the present invention has a lower WWGGC and producesless greenhouse gas emissions during the production and consumption ofthe fuel. Furthermore, by blending a low carbon diesel fuel to atraditional petroleum derived diesel fuel, the performancecharacteristics of the blended fuels in accordance with the presentinvention, such as lubricity and cetane number, are improved compared tothe traditional petroleum derived fuel.

Examples of embodiments of the invention are illustrated using figuresand are described below. The figures described herein are used toillustrate embodiments of the invention, and are not in any way intendedto limit the scope of the invention.

Referring more specifically to the drawings, FIG. 1 illustrates aschematic flow diagram, starting from the production of syngas from arenewable biomass feedstock (in Block A) to the blending of a low carbonfuel produced from the syngas with a petroleum fuel (in Block F).

A. Syngas Production

In FIG. 1, block A (110) refers to any process that produces syngas.Syngas can be generated from a wide variety of renewable biomasssources. These include, for example, cellulosic waste materials such asagricultural wastes, vegetative wood waste, energy crops, treetrimmings, and others. A suitable syngas generator can be used tothermally convert a carbonaceous feedstock to syngas. Examples of syngasgenerators and systems include pyrolyzers, gasifiers, steam orhydro-gasification systems, steam reformers, autothermal reformers orcombinations of these technologies. Syngas can also be generated fromreforming biogas, CO₂, and other renewable gas resources.

Any suitable system and apparatus can be used to generate syngas fromrenewable biomass feedstocks and to catalytically convert the syngas toa low carbon fuel. In one embodiment, an integrated system can be usedwhere the system is configured to generate liquid fuels, electricity,and heat from carbonaceous feedstocks. Such a system is described incopending U.S. patent application Ser. No. 11/966,788, filed on Dec. 28,2007 (published as US2010/0175320), which is incorporated herein byreference in its entirety.

In the integrated system described in copending U.S. patent applicationSer. No. 11/966,788, the process for producing syngas and subsequentliquid fuels are optimized by using an on-line computer system with theuse of one or more continuous gas analyzers to measure gasconcentrations and process algorithms to control and maximize productuse and energy efficiency. The characteristics of syngas can be analyzedby gas analyzers (e.g., mass spectrometer) and the carbon monoxide andhydrogen ratios can be adjusted by varying operating conditions of thesyngas production process. The gas analyzers can measure concentrationsof various gas species, such as oxygen, nitrogen, hydrogen, carbonmonoxide, and others.

In some embodiments, the system can convert a renewable biomassfeedstock to syngas, where the conversion system uses steam reforming inthe absence of oxygen or air to produce syngas. Excluding oxygen and airfrom the pyrolyzer or steam reformer can significantly decreasecontaminants typically found in the syngas (which may include hydrogensulfide, ammonia, chlorides, or particulates) that reduce catalystlifetime. Ideally, the oxygen concentration in the conversion system isno more than 0.05 Mole percent. System temperature and pressure can bealtered to limit the levels of oxygen or air in the system. For example,if the oxygen level is greater than 0.5 Mole percent, the systempressure and temperature are altered to reduce the oxygen level. Thehigher system pressures also limit the air entrained in biomassfeedstock or other feed stream from entering the system.

Other suitable systems may also be used in the production of syngas fromrenewable biomass feedstocks.

B. Syngas Cleanup and Conditioning

In FIG. 1, block B (120) represents syngas cleanup and conditioningprocesses. Clean syngas, free of impurities (which may affect catalystperformance and lifetime), allows for an efficient and economicaloperation. Impurities may include hydrogen sulfide, ammonia, chlorides,and other contaminants that result from a syngas production process.Syngas cleanup processes are well known and described in the art. Forexample, syngas cleanup processes may include sulfur clean up catalysts,particulate filters, catalytic reformation using catalysts (includingnickel based catalysts), tar cracking, and other technologies to produceclean syngas for subsequent conversion to fuels or chemicals. In certainembodiments, syngas cleanup and conditioning processes may be includedin the syngas generation system.

C. Catalytically Reacting Syngas to Produce Hydrocarbon Products

In FIG. 1, block C (130) represents conversion of syngas into variousproducts. For instance, a clean syngas stream (e.g., CO, H₂, CH₄, CO₂and H₂O at varying concentrations) is introduced to a catalytic reactorto generate liquid fuels from CO and H₂ among other products. Thecatalytic hydrogenation of carbon monoxide produce light gases, liquidsand waxes, ranging from methane to heavy hydrocarbons (C₂₅ and higher)in addition to oxygenated hydrocarbons. This process is typicallyreferred to as Fischer-Tropsch synthesis. The Fischer-Tropsch synthesisis used to produce distillate fuels (e.g., gasoline, diesel, aviationfuel, and others) or specialty chemicals (e.g. higher alcohols,paraffins, olefins, and others) from syngas.

In Fischer-Tropsch synthesis, the hydrocarbon product selectivitydepends on diffusion, reaction, and convection processes occurringwithin the catalyst pellets (i.e., supported catalyst) and reactor. Inembodiments of the invention, catalyst support or pellets can have anysuitable shapes. For example, the catalyst shape may be an extrudatewith a lobed (e.g., tri-lobes, quad-lobes, and others), fluted, or vanedcross section but can be a sphere, granule, powder, or other supportthat allows efficient operation. For lobed supports, the effectivepellet radius (i.e., the minimum distance between the mid-point and theouter surface portion of the pellet) may be about 600 microns or less,or about 300 microns or less.

In certain embodiments, the catalyst support material may be porous, andthe mean pore diameter of the support material may be greater than about100 angstroms, and in some instances, greater than about 120 angstroms.The catalyst support ideally has a crush strength of between about 3lbs/mm and 4 lbs/mm and a BET surface area of greater than about 150m²/g. By contrast, conventional high surface area supports typicallyhave an average pore diameter of less than 100 angstroms.

Supports that have a large average pore volume greater than about 120angstroms generally have a surface area much lower than 150 m²/g and acrush strength below 2 lbs/mm despite additional calcination or heattreatment. In embodiments of the invention, this can be achieved withthe addition of a structural stabilizer that provides additionalcrystallinity (for example silicon or silica oxide). This provides morestrength upon heat treatment.

Any suitable material can be used as a support material in theFischer-Tropsch process. These include metal oxides, such as alumina,silica, zirconia, magnesium, or combinations of these materials.Preferably, alumina is used as a support material to make a supportedcatalyst.

The catalytically active metals, which are included with or dispersed tothe support material, include substances which promote the production ofhydrocarbon fuel in the Fischer-Tropsch reaction. For example, thesemetals include cobalt, iron, nickel, or any combinations thereof.Various promoters may be also added to the support material. Examples ofpromoters include ruthenium, palladium, platinum, gold, nickel, rhenium,or any combinations thereof. The active metal distribution or dispersionon the support is ideally between about 2% and about 10%, preferablyabout 4%.

In one embodiment, a supported catalyst includes cobalt, iron, or nickeldeposited at between about 5 weight % and 30 weight % on gamma alumina,more typically about 20 weight % on gamma alumina, based on the totalweight of the supported catalyst. Also, the supported catalystformulation includes selected combinations of one or more promotersconsisting of ruthenium, palladium, platinum, gold nickel, rhenium, andcombinations in about 0.01-2.0 weight % range, more typically in about0.1-0.5 weight % range per promoter. Production methods of the catalystinclude impregnation and other methods of production commonly used inthe industry and are described in the art.

In embodiments of the invention, a low temperature, in-situ reductionprocedures are used to prepare catalysts. In one embodiment, thecatalyst is reduced in-situ in the multi-tubular fixed bed reactor attemperatures below 550° F. Typical Fischer-Tropsch catalysts are reducedex-situ (before loading into the reactor) and at temperatures above 600°F., and can be as high as 400° C. (750° F.).

In one embodiment, a syngas stream is reacted with a supported catalystunder specific operating conditions to produce a product streamcomprising light gases, diesel fuel and a wax, where a ratio of thediesel fuel to wax in the product stream between about 5:1 to about 30:1by weight. Typically, the ratio of the diesel fuel to wax in the productstream is at least about 8:1. In this catalytic reaction, the pressuresare typically kept below about 250 psi, more typically around 200 psi.The reaction is also operated at temperatures between about 350° F. and460° F., more typically around 410° F.

Other details of catalysts and operating conditions for convertingsyngas into hydrocarbon products are described in application Ser. No.12/927,242 filed Nov. 10, 2010 (Att. Docket No. PR-004.02), entitled“Catalytic Process for the Direct Production of Hydrocarbon Fuels fromSyngas,” which is herein incorporated by reference in its entirety.

D. Hydrocarbon Fuel Separation and Upgrading Processes

In FIG. 1, block D (140) includes product separation processes whereby aliquid fuel (e.g., a low carbon diesel fuel) is separated from otherproducts. For example, liquid and wax products are condensed out of aproduct gas stream and the light gases are recycled back to thecatalytic reactor and/or may be used for power production or otherparasitic load requirements. Block D may also include condensing out theproduct gas stream into a product mixture comprising a low carbon fuel(e.g., diesel derived from renewable biomass feedstock), water, and waxin a single knock out vessel wherein the wax stays entrained in thewater fraction for ease of separation from the low carbon fuel fraction.

The products produced from the process described in step C may beupgraded to produce a desired fuel fraction. Upgrading may be conductedon a liquid product (typically a C8-C24 fuel fraction), light gasfraction (typically a C4-C7 gas fraction), or a solid “wax” fraction(typically a C25+ solid wax fraction). Upgrading processes may includehydrocracking, hydroisomerization, distillation, thermal cracking,hydroprocessing, or other known and emerging upgrading processes.

E. Conditioning Step

In FIG. 1, block E (150) represents an optional step or steps tocondition a low carbon fuel to further improve its properties. Forexample, a fuel product steam can be exposed to a platinum promoted mildisomerization catalyst under mild process conditions. This process stepconverts some n-paraffins in the C₈-C₂₄ fraction to iso-paraffins inorder to improve cold flow properties of the fuel (e.g., a low carbondiesel fuel) which may be required in some market areas. Alternatively,in block E, a small percentage of a cold flow improver may be blendedinto the low carbon fuel fraction in order to help cold flow propertiesof the fuel for use in cold climates.

F. Blending a Low Carbon Fuel with a Petroleum Fuel

In block F (170) of FIG. 1, a petroleum fuel is blended with a lowcarbon fuel produced from a renewable biomass feedstock. The low carbonfuel separated in block D (140) (or from block E (150), if the lowcarbon fuel is further processed to improve its properties) may beblended from a petroleum fuel from block G (160). Any suitable amount ofa low carbon fuel may be added to the petroleum fuel. For example, about5% to about 90%, by volume, of a petroleum fuel may be mixed with about95% to about 10%, by volume, of a low carbon fuel produced from arenewable biomass feedstock. Typically, at least about 5%, 10%, 15%,20%, 25%, 30%, 40%, 50%, 60%, 70%, or 75% or more, by volume, of a lowcarbon fuel is blended with the rest of balance from the petroleum fuel.The mixing proportion of a low carbon fuel and a petroleum fuel maydepend on various factors, including the level of WWGGC reduction orperformance characteristics desired in the blended fuel (e.g.,lubricity, cetane number, sulfur content, and others). In someinstances, more than one type of low carbon fuels may be blended with apetroleum fuel. For example, a petroleum fuel may be blended with amixture of low carbon diesel fuels derived from two or more differenttypes of renewable sources. Blending methods may include splashblending, mixing, blending in fuel trucks, or other known and emergingmethods.

Blended fuels according to embodiments of the invention have a number ofperformance characteristics measurable by ASTM tests which are superiorcompared to the corresponding characteristics of the petroleum fuel. Forexample, a blended fuel in accordance with embodiments of the inventionmay have a cetane number which is greater than about 55, 60, 65, 70, 75,or higher.

In another example, a blended fuel in accordance with the presentinvention can have a HFRR lubricity value of less than about 500 micronsin wear scar diameter. In some instances, a HFRR lubricity value may beless than about 450 microns, 400 microns, 350 microns, 300 microns, 250microns, 200 microns, or less.

In yet another example, a blended fuel in accordance with the presentinvention can have a sulfur content of less than 10 ppm, 5 ppm, 2 ppm, 1ppm, 100 ppb, of or less.

To further illustrate embodiments of the present invention, thefollowing examples are provided.

Example #1

In this example, a synthetic diesel fuel is produced from a renewablebiomass feedstock. Agricultural wastes, including rice hulls, are usedas a feed to a pyrolysis/steam reforming system to convert the feed intosyngas. The system is operated in the absence of oxygen or air toproduce syngas. The pyrolysis process is operated at 1450° F. and thebiomass achieves a residence time of up to 20 minutes. Followingpyrolysis, a steam reforming process is operated at 1800° F. and thepyrolysis products achieve a residence time of about 5 seconds orgreater. Both pyrolysis and steam reforming are operated at a pressureof 30 psi.

The syngas feed is then introduced into a multi-tubular fixed bedreactor of a tube which includes supported catalysts. The catalyst bedis operated at a pressure of 400 psi and a temperature of 410° F.

The WWGGC of the synthetic diesel fuel is calculated according to theGREET model. The synthetic diesel fuel produced according to thisexample has a lifecycle greenhouse gas score (e.g., WWGGC) that is 89%lower than traditional, petroleum derived diesel fuel or approximately42 gCO₂e/mi (all WWGGC scores referenced in this document are calculatedusing version 1.8d.1 of the GREET model). The synthetic diesel fuel isblended at 15%, by volume, with the balance as petroleum derived dieselfuel. The resulting blend stock reduces the greenhouse gas score by13.4% over petroleum derived diesel fuel alone.

In addition, the synthetic diesel fuel has a cetane number that is 76(traditional California petroleum diesel fuels have a cetane number ofabout 45). The cetane number can be measured according to ASTM D-613specification. The low carbon synthetic diesel fuel has a cetane numberwhich is 68% higher than a cetane number of a traditional petroleumdiesel fuel. When the low carbon synthetic diesel fuel is blended at15%, by volume, with the rest of balance from a petroleum diesel fuel,the blended fuel has a cetane number which is at least 10% higher thanthe cetane number of the petroleum diesel fuel.

A lubricity value of a fuel is measured according to ASTM D 6079. Thesynthetic diesel fuel has a lubricity value of 360 (traditionalCalifornia petroleum diesel fuels have a lubricity value of about 550).The synthetic diesel fuel has a lubricity value which is about 35%better than that of the California petroleum diesel fuel. When the lowcarbon synthetic diesel fuel is blended at 15%, by volume, with the restof the balance from a petroleum diesel fuel, the blended fuel has alubricity value which is at least 5% better than the petroleum dieselfuel.

Example #2

The synthetic diesel fuel produced in example #1 is blended in varyingproportions with a California #2 diesel fuel (CA2), which is a lowsulfur diesel fuel sold throughout California. The synthetic diesel fuelis blended at 25%, 50%, and 75%, by volume, with the rest of the balancefrom the CA2 fuel. The cetane numbers of various blends are measuredaccording to ASTM D613.

As shown in FIG. 2, the 100% CA2 fuel has a cetane number of 44. The100% synthetic diesel fuel has a cetane number of 76. When 75% (byvolume) of synthetic diesel fuel is blended with 25% (by volume) of CA2fuel, the cetane number of the blend is 74. When the synthetic dieselfuel and the CA2 fuel is blended in equal proportions by volume (i.e.,50%/50%), the cetane number is about 71 which is only slightly lowerthan the cetane number of 100% synthetic diesel fuel. When 25% (byvolume) of synthetic diesel fuel is blended with 75% (by volume) of CA2fuel, the cetane number of the blended fuel is 54.

The cetane number of the blend increases non-linearly as the proportionof the synthetic diesel fuel becomes higher in the blend. It issurprising to find that when 75% of the synthetic diesel fuel is blendedwith 25% of the CA2 fuel, the cetane number of the blend is close to the100% synthetic diesel fuel as shown in FIG. 2.

Example #3

The low carbon synthetic diesel fuel produced in example #1 is blendedin varying proportions with a CA2 fuel. The synthetic diesel fuel isblended at 25%, 50%, and 75%, by volume, with the rest of the balancefrom the CA2 fuel. The lubricity value of various blends was measuredaccording to ASTM D 6079 which measures lubricity of diesel fuels by thehigh frequency reciprocating rig (HFRR).

As shown in FIG. 3, adding the synthetic diesel fuel to the CA2 fuelnon-linearly impacts the lubricity value of the blended fuel. The 100%CA2 fuel had a HFRR wear scar diameter of about 550 microns, which issubstantially higher than a HFRR wear scar diameter of the syntheticdiesel fuel, which is about 360 microns. When the synthetic fuel isblended at 25% by volume with the CA2 fuel at 75% by volume, thelubricity value of the blended fuel is reduced to a HFRR wear scardiameter of about 480. Thus, blending 25% by volume of synthetic dieselfuel reduced the HFRR wear scar diameter by about 35%. When thesynthetic fuel is blended at 50% by volume with the CA2 fuel at 50% byvolume, the blended fuel has a HFRR wear scar diameter of about 420.When 25%, by volume, of the synthetic fuel is blended with 75%, byvolume, of the CA2 fuel, the blended fuel has a HFRR wear diameter ofabout 390. Thus, blending greatly impacts the lubricity of the blendedfuel when 25% of the synthetic fuel is added.

Comparative Example #3

Instead of using the synthetic diesel fuel produced in Example #1, atraditional biodiesel is blended with the CA2 fuel. The biodiesel isobtained by trans-esterification of fats or oils, such as soybean oils.

The biofuel is blended in varying proportions with the CA2 fuel. Thesynthetic diesel fuel is blended at 25%, 50%, and 75%, by volume, withthe rest of the balance from the CA2 fuel. The lubricity values ofvarious blends are measured according to ASTM D 6079 which measureslubricity of diesel fuels by the high frequency reciprocating rig(HFRR).

The results are shown in FIG. 4. The 100% CA2 fuel has a HFRR wear scardiameter of about 550 microns. The 100% biodiesel has a HFRR wear scardiameter of about 549 microns. When the two fuels are blended atdifferent proportions (i.e., 25%, 50%, or 75% of biodiesel fuel with thebalance from the CA2 fuel), adding the traditional biofuel provides noor low improvement on lubricity values of the blends.

Although the description above contains many details, these should notbe construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. Therefore, it will be appreciated that the scope ofthe present invention fully encompasses other embodiments which maybecome obvious to those skilled in the art, and that the scope of thepresent invention is accordingly to be limited by nothing other than theappended claims, in which reference to an element in the singular is notintended to mean “one and only one” unless explicitly so stated, butrather “one or more.” All structural, chemical, and functionalequivalents to the elements of the above-described preferred embodimentthat are known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe present claims. Moreover, it is not necessary for a device or methodto address each and every problem sought to be solved by the presentinvention, for it to be encompassed by the present claims. Furthermore,no element, component, or method step in the present disclosure isintended to be dedicated to the public regardless of whether theelement, component, or method step is explicitly recited in the claims.No claim element herein is to be construed under the provisions of 35U.S.C. 112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for.”

1. A blended fuel comprising: (a) about 5% to about 90%, by volume, of apetroleum fuel; and (b) about 95% to about 10%, by volume, of a lowcarbon fuel produced from a renewable biomass feedstock, using athermochemical or biochemical conversion process, wherein the low carbonfuel has a well-to-wheels greenhouse gas content which is at least about50% lower than a well-to-wheels greenhouse gas content of the petroleumfuel, and the low carbon fuel has at least two performancecharacteristic values measurable by ASTM tests which are at least about30% improved than corresponding performance characteristic values of thepetroleum fuel; and wherein the blended fuel has a well-to-wheelsgreenhouse content which is at least 5% lower than the well-to-wheelsgreenhouse gas content of the petroleum fuel, and the blended fuel hasat least two performance characteristic values measurable by ASTM testswhich are at least about 5% improved than corresponding performancecharacteristic values of the petroleum fuel. 2-20. (canceled)
 21. Ablended fuel comprising: a) a petroleum fuel; and b) n low carbon fuelwherein the low carbon fuel is a hydrocarbon that has a well-to-wheelsgreenhouse gas content which is at least about 50% lower than awell-to-wheels greenhouse gas content of the petroleum fuel, and the lowcarbon fuel has a sulfur content of less than 5 ppm and a cetane numbergreater than 65; and wherein the blended fuel has a well-to-wheelsgreenhouse gas content which is at least 5% lower than thewell-to-wheels greenhouse gas content of the petroleum fuel, and theblended fuel has at least two performance characteristic values selectedfrom a group of performance characteristic values consisting of cetanenumber and sulfur content which are at least about 5% improved thancorresponding performance characteristic values of the petroleum fuel,wherein the blended fuel is a non-ester hydrocarbon fuel that meets thespecification of ASTM D975.
 22. The blended fuel of claim 21, whereinthe low carbon fuel is a renewable biomass feedstock-based fuel.
 23. Theblended fuel of claim 22, wherein the renewable biomass feedstockcomprises one or more of the following: renewable plant material, wastematerial, animal fats, oils and greases.
 24. The blended fuel of claim23, wherein the low carbon fuel is a hydroprocessed renewable biomassfeedstock-based fuel.
 25. The blended fuel of claim 21, wherein theoxidative stability of the low carbon fuel is at least about 30%improved over the oxidative stability of the petroleum fuel, and whereinthe oxidative stability of the blended fuel is at least about 5%improved over the oxidative stability of the petroleum fuel.
 26. Theblended fuel of claim 21, wherein the lubricity of the low carbon fuelis at least about 30% improved over the lubricity of the petroleum fuel,and wherein the lubricity of the blended fuel is at least about 5%improved over the lubricity of the petroleum fuel.
 27. A process forproducing a blended fuel comprising: a) hydroprocessing renewablebiomass thereby converting it into a low carbon fuel; b) blending thelow carbon fuel with a petroleum fuel wherein the low carbon fuel has awell-to-wheels greenhouse gas content which is at least about 50% lowerthan a well-to-wheels greenhouse gas content of the petroleum fuel, andthe low carbon fuel has a sulfur content of less than 5 ppm and a cetanenumber greater than 65; and wherein the blended fuel has awell-to-wheels greenhouse gas content which is at least 5% lower thanthe well-to-wheels greenhouse gas content of the petroleum fuel, and theblended fuel has at least two performance characteristic values selectedfrom a group of performance characteristic values consisting of cetanenumber and sulfur content which are at least about 5% improved thancorresponding performance characteristic values of the petroleum fuel,wherein the blended fuel meets the specification of ASTM D975.
 28. Theprocess of claim 27, wherein the renewable biomass comprises one or moreof the following: renewable plant material, waste material, animal fats,oils and greases.
 29. The process of claim 27, wherein the renewablebiomass is animal fats.
 30. The process of claim 27, wherein therenewable biomass is oils or greases.
 31. A blended fuel consistingessentially of: a) a petroleum fuel; and b) a low carbon fuel whereinthe low carbon fuel is a hydrocarbon that has a well-to-wheelsgreenhouse gas content which is at least about 50% lower than awell-to-wheels greenhouse gas content of the petroleum fuel, and whereinthe low carbon fuel has a sulfur content of less than 5 ppm and a cetanenumber greater than 65; and wherein the blended fuel has at least twoperformance characteristic values selected from a group of performancecharacteristic values consisting of cetane number and sulfur contentwhich are at least about 5% improved than corresponding performancecharacteristic values of the petroleum fuel, wherein the blended fuel isa non-ester hydrocarbon fuel that meets the specification of ASTM D975.32. The blended fuel of claim 31, wherein the low carbon fuel is arenewable biomass feedstock-based fuel.
 33. The blended fuel of claim32, wherein the renewable biomass feedstock is one or more of thefollowing: renewable plant material, waste material, animal fats, oilsand greases.
 34. The blended fuel of claim 31, wherein the low carbonfuel is a hydroprocessed renewable biomass feedstock-based fuel.
 35. Theblended fuel of claim 31, wherein the oxidative stability of the lowcarbon fuel is at least about 30% improved over the oxidative stabilityof the petroleum fuel, and wherein the oxidative stability of theblended fuel is at least about 5% improved over the oxidative stabilityof the petroleum fuel.
 36. The blended fuel of claim 31, wherein thelubricity of the low carbon fuel is at least about 30% improved over thelubricity of the petroleum fuel, and wherein the lubricity of theblended fuel is at least about 5% improved over the lubricity of thepetroleum fuel.
 37. The blended fuel of claim 34, wherein the renewablebiomass feedstock is animal fats.
 38. The blended fuel of claim 34,wherein the renewable biomass feedstock is oils or greases.